Some scientists fear that the Earth's weakening magnetic field could mean Earth is heading for a pole reversal. The Earth's magnetic field has persisted for billions of years, though its polarity has flipped many times. Earth’s magnetic field is pretty adept at flipping polarity. Every several hundred thousand years or so, Earth's magnetic field dramatically shifts and reverses its polarity. The poles have swapped, reversing north and south, many times over the planet’s history. Above: Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals.
When set spinning, the setup mimics the roiling liquid iron in the Earth’s outer core, which forms electrical currents that generate the magnetic field in a process called a dynamo. An ancient tree, the first and perhaps only specimen that exists, shows evidence of a reversal of Earth’s magnetic field. The Agathis Australis, known as a Kauri tree in Māori, was unearthed during the expansion of a geothermal power plant on North Island. And, as a bonus, Tahiti could be a great place to see the Northern Lights. Field Flipping. That would mean the north and south magnetic poles would switch places. Earth's Magnetic Field Went Completely Haywire During Last Reversal and Took 22,000 Years to Get Back to Normal Yet, largely hidden from daily life, the field drifts, waxes and wanes. On the right is the sort of complicated magnetic field Earth has during the upheaval of a reversal.